Hi all,
Because of an ongoing exhaust problem I am considering changing my Nanni 4-60 turbo back to the normally aspirated 50 hp engine. I understand that means a new prop but the rest looks just mechanical as the N60 is the same engine as the N50 with a turbo fitted.
The exhaust problem is corrosion at the seawater injection point, the engine has only 99 hours since new and the injection elbow has been repaired twice. I think the problem has something to do with the fact that the water lock is level with engine and not below as is preferred. The water lock capacity is larger than the 50 hp model and as a result won't fit in the only avaiable space lower than the engine. The 76 mm exhaust hose also takes up valuable storage space.
I put a ball valve between the exhaust outlet and the waterlock which, after the engine is shut down, drains any excess water into the bilge and prevents any water from flowing back up into the engine but the corrosion has returned, so I'm out of ideas.
I fitted the new engine as a replacement for a 50 hp Perkins so I figure the power loss is not going to dramatically affect the boats performance.
I chose and fitted the engine and because I'm not a mechanic I might have missed something basic during the exercise.
Any thoughts would be greatly appreciated!
The corrosion is caused by the hot seawater meeting the exhaust. It will still be there if you remove the turbo. Keep the turbo and investigate a better injection elbow. Draining the water lock just adds more water to the bilge and slows the filling of the water lock after the next start up.
Maybe there is a different style of water lock on the market that may fit better (lower) for your installation.
I would be surprised if the engine runs after removing the turbo. Although the block and crank might be the same, a turbo generally runs a lower compression ratio with different pistons or head shape. If the problem is with the exhaust, I would focus on finding a solution for the exhaust elbow and leave the engine alone.
Select to expand quoteLibran said...
I would be surprised if the engine runs after removing the turbo. Although the block and crank might be the same, a turbo generally runs a lower compression ratio with different pistons or head shape. If the problem is with the exhaust, I would focus on finding a solution for the exhaust elbow and leave the engine alone.
Agree. A turbo engine isn't the same as a normally aspirated engine of the same type. There are numerous differences. I doubt you can do it.
I'd follow Ramona's suggestion.
One thing you may be over looking if shut down time meaning a turbo creates far more temp than a normal aspirated engine in earth moving the ECMs can control the shut down time which I usually set at 5 minutes before the engine is turned off. I'm not saying you don't do this nor am I saying its a solution just making you aware.
You would have fitted a anti siphon valve as well as the manual states it should have one.
Ill think on it also Ill be back
a photo would be nice to see your exhaust set up
I assuming its this motor and gear box set up?
www.nannienergy.com/downloads/manuals/N4.85-N4.100/Manuel%20N4.85-N4.100%20ENG%20-%20970316089.pdf
Hi you could relocate the turbo lower that would give you the space for a taller exhaust riser
I've turbo charged a few cars In the past and nothing is impossible it was always much harder to get road legal for rego.
just make Shure the turbo isn't to low or the oil will not drain and plum every thing up. there would be some metal fabrication required but most auto exhaust shop`s could handle it
if you do remove your turbo you would have to keep a close eye on the exhaust gas temps .high temps caused by over fueling will destroy any diesel and a over pitched propeller would make it much worse.
I would assume the turbo fuel pump would at least have larger internals and a boost compensator
it would need to be replaced or retuned
engine timing would also need to be retuned
and possible new nozzles for the injector's
compression would most likely be the same but it would be worth checking with the manufacturer
turbo engine`s do run smother too
Does Beta marine offer the same engine (Kubota) in turbo form? if so perhaps replacing the exhaust elbow with the Beta one.
I was told by a mate, who chose a smaller Beta engine a few years ago, over the Nanni equivalent, that the Beta marinisation had fewer issues with corrosion.
I have also been looking at replacing my Perkins 4108
Select to expand quoteAmbler said..
Does Beta marine offer the same engine (Kubota) in turbo form? if so perhaps replacing the exhaust elbow with the Beta one.
I was told by a mate, who chose a smaller Beta engine a few years ago, over the Nanni equivalent, that the Beta marinisation had fewer issues with corrosion.
I have also been looking at replacing my Perkins 4108
rebuild it 
Select to expand quoteAmbler said..
Does Beta marine offer the same engine (Kubota) in turbo form? if so perhaps replacing the exhaust elbow with the Beta one.
I was told by a mate, who chose a smaller Beta engine a few years ago, over the Nanni equivalent, that the Beta marinisation had fewer issues with corrosion.
I have also been looking at replacing my Perkins 4108
The Kubota generator on my fishing vessel had a cast iron sea water injection point. It was a consumable item. The idea was for it to rot away first and be easily replaceable.
If it was my engine bay the first thing Id do would be relocate that wiring harness away from the ball valve unit. as this may bite you on the back side later on .
Years ago can recall where a alloy brake master cylinder because of the porous nature brake fluid was doing exactly the same thing oozing through the alloy.
The manufacturer ended up using Loctite this was forced into the alloy and sealed the alloy.
In some way its a warranty fault how to get to that result maybe harder than you think.
Ill think on it talk tonight.
You may need a new water lift muffler that will shift more water when running and hold more when shut down, hence lowering the water level from the engine. There was a guy in Carringbah who made fibreglass ones to suit. He advertised in Afloat magazine. I had one made about 12 years ago that replaced the Vetus one that was on the boat. A great improvement.
Great idea to flush with fresh, I used to do that on my previous boats engine a raw water cooled yanmar. It extended the life of the annodes greatly.
Also a good idea to drain off the muffler if it is storing too much water.
HGo2,
I hear what you are saying with regards to the warranty, after tiring of very slow and, not wanting to get involved type of responses to my emails from the engine supplier I contacted Nanni in France and a VERY short time after I was informed that they would supply a new exhaust elbow, which they did and its that one that is corroding now.
The engine runs well. Another minor issue is that the electrical harness that was supplied with the engine was 4 metres long and so had to be shortened. During the process of cutting the harness it was noticed that the harness was stamped automotive and the wires were not tinned as you would expect in a marinised engine.
I've heard only good reports about the Kubota engines, so hopefully once this corrosion is sorted out I can focus my attention and dollars on new or upgraded something else!
can't wait!
OK I'm confused now. I thought the problem was corrosion in the salt water injection point. Draining and flushing the exhaust wont make any difference here apart from adding more complexity to what is meant to be a simple system. When the engine is shut down the water level in this pipe will be at the height of the top of the water muffler, the salt water injection point or exhaust elbow will be dry. Draining the salt water and then flushing with fresh is just wasting time. This is if the water lock is below the height of the cylinder head and the cylinder head is above the waterline of course. There has been no mention of this yet. I like the quality hose clamps but plastic reinforced hose has no place in an engine room.
Question was the complete exhaust system O.D. upgraded completely to the exhaust out let? to complement the turbo?
Hi Guys,
Thanks for all your input. Some more details to clear the picture, the engine is below the waterline and the waterlock is below the recommended capacity by about 3 litres, when the engine is shut down some water is still in the exhaust hose because the water lock can't be placed any lower and I was worried that this water could be forced back into the engine so I fitted the drain valve to get rid of the excess water, there is not much water maybe a cupfull or two but I guess it would be enough to cause damage. The drain works well.
Because of the non complying water lock and my not being able to understand the cause of the corrosion I was thinking that the two were linked, when the first elbow corroded I suspected that it might have been simply a faulty casting and a new one would solve the problem but its hard to believe that it would happen twice, and I haven't heard of any others with the problem so I so naturally I started to think I had got something wrong along the way.
I followed all the instuctions and recomendations for the new engine installation including the back pressure measuring which came up to recommended levels.
When I mentioned the fresh water flushing it was in repy to HGO2's querey about turbo timed shutdowns. I have't actually timed it but it takes 3 or 4 minutes to fill the sink and probably another 2 to drain with the engine idling all the while, and removing salty water from the system can't do any harm. I hope.
The corrosion is from the hot seawater mixing with the exhaust. Is does not matter whether you have a turbo or not, the mixer is going to be in roughly the same place, a few inches below the exhaust valves. When the engine is shut off the water in the exhaust will drop to the highest point in the water lock muffler. The fact that some exhaust valves will be open will allow the water to drop as well as the the anti siphon valve. Draining the exhaust pipe will not remove the water from the muffler unless you have a drain in that too. There fore the pipe will always have moist air inside and this will worst than full of water if your concerned with corrosion in the engine side of the exhaust. The water lock has to be below the cylinder head.
In the picture above I would be installing the water lock muffler about where the drain ball valve is. You may have to manufacture one to fit the space to get enough capacity. I would not under any circumstance pump in fresh water into the exhaust system of a stationary motor. Some exhaust valves will be open and water may back up into the cylinder head.
I would suggest a careful read of this site, and there are plenty of others. I have not looked but I bet there are plenty of Youtube videos explaining the correct installation of turbo marine engines.
www.sbmar.com/articles/designing-a-marine-exhaust-system/
Add some details to your bio as well. You may have a lister living near by who can wander over and have a look.
Hi Windsong38
How often do you replace the anode in the exhaust elbow? Sometimes it may look ok but it may be stuffed. Check that it is there and you don't just have what looks like a bung.
